Investigations are being conducted into aspects of specialization of the primate and human retinochoroidal complex with emphasis on the pigmented epithelium. Using a cell culture system, the mitotic potential of human pigmented epithelial cells as a function of donor age, pigmented epithelial cell surface molecules, and in vitro enzymatic activity including tyrosinase are being studied. Fluorescent antibody reactions of fresh human eye tissues and cultured pigmented epithelial and choroidal cells with monospecific antibodies to purified extracellular matrix proteins are being compared in normal and pathologic tissues. In vitro characteristics of cellular outgrowth from pathologic human vitreous bands are being documented by light and electron microscopy. The role of various ocular tissue cells in the production of these bands and in traction retinal disturbances has been documented.